On a ship, the staff is used to people trying more than one dish,and perhaps asking for another because that fact. In the galley, for someone to taint a plate would be so much more difficult to do, due to the pace of getting the meals out, and, the amount of workers around.
Sending a dish back in a restaurant, due to not liking it, is a harder propostion, than, having it nor cooked properly,say.
I think the tone of the diner with the complaint sets the wheels in motion. My daughter is and has been a p/t waitress for a long time. A good rapour goes a long way, in this situation.
With the cost of dining out, if by chance something arises, I don't get why anyone would be a martyr, for the sake of politely stating the issue with the dish. The odds are overwhelmingly in the diners favor.
My old neighbor used to eat the entire lobster,then complain it was not good